The present invention relates to an expansion valve for controlling the flow rate of a refrigerant to be supplied to an evaporator in a refrigeration cycle of a refrigerator, an air conditioning device and so on.
In the prior art, this type of expansion valve is used in the refrigeration cycle of an air conditioning device in vehicles, as disclosed in Japanese Laid-Open Patent Publication No. H9-26235. FIG. 17 shows a vertical cross-sectional view of a widely used prior art expansion valve with an outline of the refrigeration cycle. FIG. 18 is a schematic view of the valve body in the expansion valve, and FIG. 19 is a front view of the expansion valve viewed from direction A of FIG. 17. The expansion valve 10 comprises a valve body 30 made of aluminum alloy and having a substantially prismatic shape, to which are formed a first passage 32 of a refrigerant pipe 11 in the refrigeration cycle mounted in the portion from the refrigerant exit of a condenser 5 through a receiver 6 toward the refrigerant entrance of an evaporator 8 through which a liquid-phase refrigerant travels, and a second passage 34 of the refrigerant pipe 11 mounted in the portion from the refrigerant exit of the evaporator 8 toward the refrigerant entrance of a compressor 4 through which a gas-phase refrigerant travels. The passages are formed so that one passage is positioned above the other passage with a distance in between. Further, in FIGS. 18 and 19, reference number 50 shows bolt inserting holes for mounting the expansion valve 10.
On the first passage 32 is formed an orifice 32a where adiabatic expansion of the liquid-phase refrigerant supplied from the refrigerant exit of the receiver 6 is to be performed. On the entrance side of the orifice 32a or upper stream side of the first passage is formed a valve seat, and a spherical valve means 32b supported by the valve member 32c from the upper stream side is positioned on the valve seat. The valve member 32c is fixed to the valve means by welding, and positioned between a biasing means 32d of a compression coil-spring and the like, thereby transmitting the bias force of the biasing means 32d to the valve means 32b, and as a result, biasing the valve means 32b toward the direction approaching the valve seat.
The first passage 32 to which the liquid-phase refrigerant from the receiver 6 is introduced acts as the passage for the liquid-phase refrigerant, comprising an entrance port 321 connected to the receiver 6, and a valve chamber 35 connected to the entrance port 321. An exit port 322 is connected to the evaporator 8. The valve chamber 35 is a chamber with a bottom formed coaxially with the orifice 32a, and is sealed by a plug 39. The plug 39 is equipped with an o-ring 39a.
Moreover, the valve body 30 is equipped with a small radius hole 37 and a large radius hole 38, which is larger than the hole 37, which penetrates through the second passage 34 and are positioned coaxial to the orifice 32a, so as to provide driving force to the valve means 32b according to the exit temperature of the evaporator 8, and on the upper end of the valve body 30 is formed a screw hole 361 to which a power element portion 36 acting as a heat sensing portion is fixed.
Further, the valve body 30 includes a narrow portion 30b having a thin width whose width size W.sub.2 is reduced (narrowed) compared to the width size W.sub.1 of the portion where the bolt holes 50 exist, at the lower portion corresponding to the first passage 32 which is opposite to the upper portion where the power element portion 36 is to be mounted. The narrow portion contributes to lighten the weight and to reduce the cost of the parts used for the valve body 30.
The base-shape material (material formed to have the basic shape) of the valve body 30 is manufactured by an extrusion process of an aluminum alloy for example, and the bolt holes 50 are formed by a following drilling process.
The power element portion 36 comprises a diaphragm 36a made of stainless steel, an upper cover 36d and a lower cover 36h welded to each other with the diaphragm 36a positioned in between so as to each define an upper pressure housing 36b and a lower pressure housing 36c forming two sealed housing on the upper and lower areas of the diaphragm 36a, and a sealed tube 36i for sealing a predetermined refrigerant working as a diaphragm driving liquid into the upper pressure housing 36b, wherein the lower cover 36h is screwed onto the screw hole 361 with a packing 40. The lower pressure housing 36c is communicated to the second passage 34 through a pressure-equalizing hole 36e formed coaxial to the center axis of the orifice 32a. The refrigerant vapor from the evaporator 8 flows through the second passage 34, and therefore, the second passage 34 acts as a passage for the gas-phase refrigerant, and the pressure of the refrigerant gas is loaded to the lower pressure housing 36c through the pressure-equalizing hole 36e. Further, reference number 342 represents an entrance port from which the refrigerant transmitted from the evaporator 8 enters, and 341 represents an exit port from which the refrigerant transmitted to the compressor 4 exits.
Inside the lower pressure housing 36c contacting the diaphragm 36a is formed an aluminum heat sensing shaft 36f positioned slidably inside the large radius hole 38 penetrating the second passage 34, so as to transmit the refrigerant exit temperature of the evaporator 8 to the lower pressure housing 36c and to slide inside the large radius hole 38 in correspondence to the displacement of the diaphragm 36a accompanied by the difference in pressure between the lower pressure chamber 36c and the upper pressure chamber 36b in order to provide drive force, and a stainless steel operating shaft 37f having a smaller diameter than the heat sensing shaft 36f is positioned slidably inside the small radius hole 37 for pressing the valve means 32b against the elastic force of the biasing means 32d in correspondence to the displacement of the heat sensing shaft 36f, wherein the heat sensing shaft 36f is equipped with a sealing member, for example, an o-ring 36g, so as to secure the seal between the first passage 32 and the second passage 34. The upper end of the heat sensing shaft 36f contacts the lower surface of the diaphragm 36a as the receiving portion of the diaphragm 36a, the lower end of the heat sensing shaft 36f contacts the upper end of the operating shaft 37f, and the lower end of the operating shaft 37f contacts the valve means 32b, wherein the heat sensing shaft 36f together with the operating shaft 37f constitute a valve drive shaft. Accordingly, the valve drive shaft extending from the lower surface of the diaphragm 36a to the orifice 32a of the first passage 32 is positioned coaxially inside the pressure-equalizing hole 36e. Further, a portion 37e of the operating shaft 37f is formed narrower than the inner diameter of the orifice 32a, which penetrates through the orifice 32a, and the refrigerant passes through the orifice 32a.
A known diaphragm drive liquid is filled inside the upper pressure housing 36b of the pressure housing 36d, and through the diaphragm 36a and the valve drive shaft exposed to the second passage 34 and the pressure equalizing hole 36e communicated to the second passage 34, the heat of the refrigerant vapor travelling through the second passage 34 from the refrigerant exit of the evaporator 8 is transmitted to the diaphragm drive liquid.
In correspondence to the heat being transmitted as above, the diaphragm drive liquid inside the upper pressure housing 36b turns into gas, the pressure thereof being loaded to the upper surface of the diaphragm 36a. The diaphragm 36a is displaced to the vertical direction according to the difference between the pressure of the diaphragm drive gas loaded to the upper surface thereof and the pressure loaded to the lower surface thereof.
The vertical displacement of the center area of the diaphragm 36a is transmitted to the valve means 32b through the valve drive shaft, which moves the valve means 32b closer to, or away from, the valve seat of the orifice 32a. As a result, the flow rate of the refrigerant is controlled.
Accordingly, the temperature of the low-pressure gas-phase refrigerant sent out from the exit of the evaporator 8 is transmitted to the upper pressure housing 36b, and according to the temperature, the pressure inside the upper pressure housing 36b is changed. When the exit temperature of the evaporator 8 rises, in other words, when the heat load of the evaporator is increased, the pressure inside the upper pressure housing 36b is raised, and correspondingly, the heat sensing shaft 36f or valve drive shaft is driven to the downward direction, pushing down the valve means 32b. Thereby, the opening of the orifice 32a is widened. This increases the amount of refrigerant being supplied to the evaporator 8, and lowers the temperature of the evaporator 8. In contrast, when the temperature of the refrigerant sent out from the evaporator 8 is lowered or heat load of the evaporator is reduced, the valve means 32b is driven to the opposite direction, narrowing the opening of the orifice 32a, reducing the amount of refrigerant being supplied to the evaporator, and raises the temperature of the evaporator 8.
The expansion valve 10 is mounted by bolt holes 50 to a predetermined member. FIG. 20 is a view explaining the mounting structure thereof, and in the drawing, a mounting member 60 is formed to have a plate-like shape, supporting two pipes 62 and 64. The pipe 62 is a pipe communicated to the compressor 4, and a tip portion 62a thereof is inserted to a port 341. In such state, a seal is formed between the pipe and the port by a seal ring 62b. The second pipe 64 is communicated to the receiver 6, and a tip portion 64a thereof is inserted to a port 321 through a seal 64b. A mounting member 70 is formed to have a plate shape, supporting two pipes 72 and 74.
The pipe 72 is communicated to the exit of the evaporator 8, and a tip portion 72a thereof is inserted to a port 342 through a seal 72b. The pipe 74 is communicated to the entrance of the evaporator 8, and a tip portion 74a thereof is inserted to a port 322 through a seal 74b. When fixing these mounting members 60 and 70 onto the body of the expansion valve 10, a bolt 80 is inserted to a bolt hole 66 formed on the mounting member 60. The bolt 80 is further inserted to a bolt hole 50 on the expansion valve 10 so as to penetrate therethrough, and a screw portion 82 on the tip of the bolt 80 is screwed onto a screw portion 76 of the second mounting member 70. By screwing the bolt 80, the tip portions of each pipes on each mounting member are inserted to respective ports of the expansion valve, and the fixing is completed. Further, the bolt hole 50 on the other side is also similarly fixed.
Moreover, in the prior art expansion valve, a plug body 36k may be used to seal the predetermined refrigerant as shown in FIG. 21 instead of using the sealed tube 36i as shown in FIG. 17. For example, a stainless steel plug body 36k may be inserted to a hole 36j formed on the upper cover 36d made of stainless steel so as to cover the hole, and the plug body 36k maybe fixed to the hole 36j by welding. Further, the operation for controlling the flow rate of the refrigerant by the valve is similar to that of FIG. 17, so FIG. 21 only shows the area related to the power element portion 36. FIG. 22 shows the schematic view of the valve body similar to FIG. 18 of the expansion valve but when the seal is performed by the plug body 36k, and the same reference numbers show the same components. In FIGS. 18 and 19, the sealed tube 36i is omitted.